A. Field of the Invention
The field of the invention relates generally to greenhouse lighting fixtures, and more particularly to an improved LED greenhouse light fixture, as well as a greenhouse that utilizes one or more of the LED light fixtures.
B. Description of Related Art
Greenhouses commonly use artificial supplemental light to encourage or promote plant growth. Typical types of greenhouse lighting systems include incandescent lights, florescent lights, and various high-intensity discharge (HID) lamps, including high-pressure sodium (HPS) lights, metal halide lights, and mercury vapor lights. Although each of these types of light has respective attributes useful for different phases of plant growth, the most predominantly used type of supplemental light has been HPS lamps, primarily because they are less expensive to purchase and operate, and have a relatively high efficiency (convert about 25% of electricity into light energy). HPS lamps are, however, not without disadvantages.
FIG. 1 illustrates a greenhouse 10 that utilizes one or more HPS lighting fixtures 28 to provide artificial light to rows of plants 14 supported above a floor 24 in grow containers 20. The greenhouse 10 has a roof 22, and the HPS lighting fixtures 28 are supported on or from frame structure members 12 in close proximity to the roof 22, as is known in the art. The HPS fixtures 28 are relatively large and it has been estimated that these fixtures 28 block about 10% of the lighted footprint of a greenhouse from receiving sunlight. The fixtures 28 are also quite heavy. A single HPS lighting fixture 28 may weigh about 40 lbs., thus requiring more robust greenhouse frame structure 12 to support the fixtures 28. The HPS lighting fixtures 28 generate noise and the bulbs have a short life. In addition, the HPS lamps generate significant radiated heat, which prevents the lamps from being placed in close proximity to the plants. Because the HPS lighting fixtures 28 are supported at relatively high heights above the plants 14, even with reflectors 30, a significant portion of the emitted light is directed to towards the floor 24 of the greenhouse in zones “A” and “B” depicted in FIG. 1 and is not absorbed by the plants, resulting in an inefficient use of the light and increased power consumption for a given measure of plant growth.
The use of intra-row greenhouse LED lighting systems has been proposed as a means to tailor supplemental light at a specific wavelength to particular target plant growth phases, as well as to increase the amount of light absorbed by the plants. LED lights produce relatively little radiated heat and can thus be placed relatively close to the plants, and various intra-row systems place the LED fixtures between the rows of plants. However, even with the use of narrow beam pattern LEDs, a substantial portion of the emitted light is still not absorbed by the plants.
Thus, an improved greenhouse lighting system fixture is desirable to address at least one of the deficiencies of present systems, particularly inefficient plant absorption of the produced light.